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title: Key Changes
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This document lists changes made to the Model Context Protocol (MCP) specification since
the previous revision, [2025-06-18](/specification/2025-06-18).

## Major changes

1. Enhance authorization server discovery with support for [OpenID Connect Discovery 1.0](https://openid.net/specs/openid-connect-discovery-1_0.html). (PR [#797](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/797))
2. Allow servers to expose icons as additional metadata for tools, resources and prompts ([SEP-973](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/973)).

## Minor changes

1. Clarify that servers must respond with HTTP 403 Forbidden for invalid Origin headers in Streamable HTTP transport. (PR [#1439](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1439))

## Other schema changes

## Full changelog

For a complete list of all changes that have been made since the last protocol revision,
[see GitHub](https://github.com/modelcontextprotocol/specification/compare/2025-06-18...draft).
